According to the Montreal Protocol on Substances that Deplete the Ozone Layer, the currently most widely used fluoroalkane, HFC-134a, which also has the most greenhouse effects (its GWP values is 1340, relative to CO2), would be gradually eliminated. In the search for substitutes for FHC-134a, 2,3,3,3-tetrafluoropropene (HFO-1234yf) has been accepted by major European automakers as a substitute for HFC-134a. In Europe, U.S. and Japan, HFO-1234yf has been approved for sale starting from Jan. 1, 2011. This compound will be used on new cars as a substitute for the third generation coolant, HFC-1234a. By Jan. 1, 2017, no automobile is allowed to use HFC-1234a. HFO-1234yf is also a monomer or co-polymer starting material for the synthesis of thermally stable and highly flexible rubber material; it has a great market potential.
Synthetic routes for HFO-1234yf are limited to the following reported processes:                Canadian Patent No. 690037 and U.S. Pat. No. 2,931,840 reported the synthesis of 2,3,3,3-tetrafluoropropene by high temperature cracking using chloromethane (CH3Cl) and tetrafluoroethylene (CF2═CF2), or chloromethane and difluorochloromethane (R22), as the starting materials.        U.S. Patent Application Publication No. 2009/253946 A1 reported a method for the synthesis of HFO-1234yf by high temperature cracking of chloromethane and trifluorochloroethylene (CF2═CFCl). This method produce substantial amounts of impurities and the yield is low.        U.S. Pat. No. 2,996,555 reported a method for the synthesis of HFO-1234yf using CX3CF2CH3 (X═Br, Cl, or F) as a starting material.        PCT Publication No. WO 2007/019355 reported a method for the synthesis of both HFO-1234yf and HFC-1234ze starting from CX3CCl═CClY (X and Y are independently selected from F or Cl).        PCT Publication No. WO 2007/117391 reported a method that uses CHF2CHFCHF2 (HFC-236ea) and CF3CHFCH2F (HFC-245eb) to produce both HFC-1225ye and HFO-1234yf.        PCT Publication Nos. WO 2008/002500 and WO 2008/030440 reported a method using CF3CF═CFH (HFC-1225ye) as a starting material to synthesize HFO-1234yf.        PCT Publication No. WO 2008/054780 reported a method using CCl3CF2CF3 (CFC-215cb) or CCl2FCF2CClF2 (CFC-215ca) as a starting material to react with H2 under the catalysis of a catalyst to synthesize a product containing HFO-1234yf.        PCT Publication Nos. WO 2008/054779 and WO 2008/060614 reported a method for the synthesis of HFO-1234yf using CHCl2CF2CF3 (HFC-225ca) or CHClFCF2CClF2 (HCFC-225cb) as a starting material.        PCT Publication Nos. WO 2008/054778 reported a method for the synthesis of HFO-1234yf by hydrogenation of CHCl2CF2CF3 (HFC-225ca).        PCT Publication Nos. WO 2008/0443 reported a method for the synthesis of HFO-1234yf by catalytic isomerization of HFC-1234ze.        U.S. Patent Application Publication No. 2009/299107 reported a method for the synthesis of HFO-1234yf using CF3CFClCH3 (HFC-244bb) as a starting material.        U.S. Patent Application Publication No. 2007/197842 reported a method for the synthesis of HFO-1234yf in three steps starting using CCl2═CClCH2Cl as a starting material.        PCT Publication Nos. WO 2009/084703 reported a method for the synthesis of HFO-1234yf using CF3CF═CF2 (HFP) as a starting material.        PCT Publication Nos. WO 2006/063069 reported a method for the synthesis of HFO-1234yf by dehydrating a starting material, 2,2,3,3,3,-pentafluoropropan-1-ol (CF3CF2CH2OH).        
Among these reported methods, the one using HCFC-1233xf as the starting material for the synthesis of HFO-1234yf represents most commercial values.
U.S. Patent Application Publication No. 2011/0160497 discloses a reaction that uses a chromium-containing fluorination catalyst and 0.1%-0.15% O2 based on the moles of HCFC-1233xf. However, the conversion rate of HCFC-1233xf reaches only about 10%. HFO-1234yf selectivity can reach 72.5%. PCT publication No. WO 2010/123154 A1 discloses a method that controls the chromium valance in the catalyst CrOm (1.5<m<3.0), i.e., by introducing 0.1-1.0 mole O2/mole HCFC-1233xf to control the valance of chromium. The reaction results show that the conversion rate of HCFC-1233xf can reach 37.8%, and the selectivity of HFO-1234yf can reach 75.2%. In these two methods, the high valance chromium is not stable and is prone to convert to the low valance chromium, leading to short life of the catalyst and the catalyst activity degrades relative fast.